Even in the books of patanjali yoga, it is said that in order to attain perfection in yoga one needs Hari-bhakti. Ultimately devotion is the perfection. Narayana Smriti at the end of one's life is perfection. Normally people end their life thinking of whatever their attached to. If we are chanting the Lord's names and engage in his service then we maintain an attachment for the Lord throughout our life. The Lord will be the common denominator and pivot point in our different activities. Whatever process one is engaging in, this remembrance of Narayana, taking shelter of the Lord is the most important aspect.
Pure devotion means that one is very eager and enthusiastic to serve the Lord at all time without any laziness.
The path of bhakti is personal, it is not ritualistically automatic.
Devotional service is so simple, but devotees because of their material inclinations make it complicated.
The Lord comes in a different form or partial form in order to deliver his devotees and generally he is always telling us how to surrender and how to serve him. If one directly serves the Lord with no condition, unconditionally "I am serving you Lord for Your pleasure, I want me to do what you want me to do". If we do things in that way the amazing thing is that the Lord becomes very pleased with us. The Supreme Lord has given us everything, what can we do for him? When we appreciate how great he is and feel grateful, that is the beginning of pure devotion. Pure devotion should be the goal of our life.
A devotee doing sense gratification out of material conditionings, if keeps on listening to pure devotees, soon becomes disgusted of sense gratification and gives it up, and so attains the pure devotion to krishna.